They have Iron dome don't they?
The invasion wasn't sparked by rocket attacks it was sparked by an invasion of hundreds of militants.
And the militants died at a roughly 1:1 ratio to each Israeli life. They knew they were on suicide missions unless they were part of the crew who went back to Gaza with hostages.
The rockets aren't particularly effective.
Israel isn't likely to be so daft to allow that kind of invasion from Gaza again.
What you are saying is that Israel has the right to kill tens of thousands of people to take out the rockets which kill only a small number of people.